We describe here three cases of pancreatitis after congenital choledochal cyst excision. In these three cases, the choledochal remnant in the pancreas head was markedly dilated, probably because of an incomplete resection of the cyst at the primary operation, and an increase in intraluminal pressure of the pancreatic duct caused by a dynamic obstruction by a protein plug or a pancreatic calculus. Complete cyst excision, including the choledochal wall in the pancreas, is therefore strongly recommended.